Projects
The Computer aspect
of HCI
• Project Phase One reports are due next
week: March 10.
• Submit a printed hard-copy of your report
in class on March 10.
• If you or your teammates cannot attend
the lecture, submit your report to Gulsah
Tumuklu at A-401 before class on March
10.
• Check the newsgroup for
announcements: looking for teammates?
etc.
The Computer
Reading assignment
• Again no reading assignment this week.
a computer system is made up of various elements
each of these elements affects the interaction
– input devices – text entry and pointing
– output devices – screen (small&large), digital paper
• Work on your project.
– virtual reality – special interaction and display devices
– physical interaction – e.g. sound, haptic, bio-sensing
– paper – as output (print) and input (scan)
– memory – RAM & permanent media, capacity & access
– processing – speed of processing, networks
Interacting with computers
to understand human–computer interaction
… need to understand computers!
A ‘typical’ computer system
•
•
•
screen, or monitor, on which there are windows
keyboard
mouse/trackpad
•
variations
window 1
window 2
– desktop
– laptop
– PDA
what goes in and out
devices, paper,
sensors, etc.
what can it do?
memory, processing,
networks
12-37pm
the devices dictate the styles of interaction that the system
supports
If we use different devices, then the interface will support a
different style of interaction
1
How many …
• computers in your house?
– hands up, …
… none, 1, 2 , 3, more!!
• computers in your pockets?
How many computers …
in your house?
– PC
– TV, VCR, DVD, HiFi,
cable/satellite TV
– microwave, cooker,
washing machine
– central heating
– security system
in your pockets?
– PDA
– phone, camera
– smart card, card with
magnetic strip?
– electronic car key
– USB memory
can you think of more?
Interactivity?
Richer interaction
Long ago in a galaxy far away … batch processing
– punched card stacks or large data files prepared
– long wait ….
– line printer output
… and if it is not right …
Now most computing is interactive
– rapid feedback
– the user in control (most of the time)
– doing rather than thinking …
sensors
and devices
everywhere
Is faster always better?
Keyboards
text entry devices
keyboards (QWERTY et al.)
chord keyboards, phone pads
handwriting, speech
• Most common text input device
• Allows rapid entry of text by experienced
users
• Keypress causes a character code to be sent
• Usually connected by cable, but can be
wireless
2
layout – QWERTY
QWERTY (ctd)
• Standardized layout
but …
– non-alphanumeric keys are placed differently
– accented symbols needed for different scripts
– minor differences between UK and USA keyboards
2
1
Q
• QWERTY arrangement not optimal for typing
– layout to prevent typewriters jamming!
• Alternative designs allow faster typing but large social
base of QWERTY typists produces reluctance to change.
4
3
W
E
S
A
Z
5
R
D
X
6
T
F
C
G
V
8
7
Y
U
H
B
J
N
K
M
0
O
P
L
,
.
SPA CE
alternative keyboard layouts
special keyboards
Alphabetic
• designs to reduce fatigue
• for one handed use
– keys arranged in alphabetic order
– not faster for trained typists
– not faster for beginners either!
9
I
e.g. the Maltron left-handed keyboard
Dvorak
–
–
–
–
–
common letters under dominant fingers
biased towards right hand
common combinations of letters alternate between hands
10-15% improvement in speed and reduction in fatigue
But - large social base of QWERTY typists produce market
pressures not to change
Chord keyboards
phone pad and T9 entry
only a few keys - four or 5
letters typed as combination of keypresses
compact size
– ideal for portable applications
short learning time
– keypresses reflect letter shape
- fast once you have trained
• use numeric keys with
multiple presses
2
3
4
5
–abc
-def
-ghi
-jkl
6
7
8
9
-
mno
pqrs
tuv
wxyz
hello = 4433555[pause]555666
surprisingly fast!
• T9 predictive entry
– type as if single key for each letter
– use dictionary to ‘guess’ the right word
BUT - social resistance, plus fatigue after extended use
NEW – niche market for some wearables
3
Handwriting recognition
Speech recognition
• Text can be input into the computer, using a
pen and a digesting tablet
• Improving rapidly
• Most successful when:
– natural interaction
• Technical problems:
– capturing all useful information - stroke path,
pressure, etc. in a natural manner
– segmenting joined up writing into individual letters
– interpreting individual letters
– coping with different styles of handwriting
• Used in PDAs, and tablet computers …
… leave the keyboard on the desk!
– single user – initial training and learns peculiarities
– limited vocabulary systems
• Problems with
–
–
–
–
external noise interfering
imprecision of pronunciation
large vocabularies
different speakers
Numeric keypads
• for entering numbers quickly:
– calculator, PC keyboard
• for telephones
not the same!!
positioning, pointing and drawing
1
2
3
7
8
9
4
5
6
4
5
6
7
8
9
1
2
3
*
0
#
0
.
=
telephone
mouse, touchpad
trackballs, joysticks etc.
touch screens, tablets
eyegaze, cursors
calculator
the Mouse
the mouse (ctd)
• Handheld pointing device
Mouse located on desktop
– very common
– easy to use
• Two characteristics
– planar movement
– buttons
(usually from 1 to 3 buttons on top, used for
making a selection, indicating an option, or to
initiate drawing etc.)
– requires physical space
– no arm fatigue
Relative movement only is detectable.
Movement of mouse moves screen cursor
Screen cursor oriented in (x, y) plane,
mouse movement in (x, z) plane …
… an indirect manipulation device.
– device itself doesn’t obscure screen, is accurate and fast.
– hand-eye coordination problems for novice users
4
How does it work?
Even by foot …
Two methods for detecting motion
• some experiments with the footmouse
– controlling mouse movement with feet …
– not very common :-)
• Mechanical
– Ball on underside of mouse turns as mouse is moved
– Rotates orthogonal potentiometers
– Can be used on almost any flat surface
• but foot controls are common elsewhere:
• Optical
–
–
–
–
– car pedals
– sewing machine speed control
– organ and piano pedals
light emitting diode on underside of mouse
may use special grid-like pad or just on desk
less susceptible to dust and dirt
detects fluctuating alterations in reflected light intensity
to calculate relative motion in (x, z) plane
Touchpad
Trackball and thumbwheels
• small touch sensitive tablets
• ‘stroke’ to move mouse pointer
• used mainly in laptop computers
Trackball
– ball is rotated inside static housing
• like an upsdie down mouse!
–
–
–
–
–
• good ‘acceleration’ settings important
– fast stroke
• lots of pixels per inch moved
• initial movement to the target
– slow stroke
Thumbwheels …
• less pixels per inch
• for accurate positioning
Joystick and keyboard nipple
Joystick
– indirect
pressure of stick = velocity of movement
– buttons for selection
on top or on front like a trigger
– often used for computer games
aircraft controls and 3D navigation
Keyboard nipple
– for laptop computers
– miniature joystick in the middle of the keyboard
relative motion moves cursor
indirect device, fairly accurate
separate buttons for picking
very fast for gaming
used in some portable and notebook computers.
– for accurate CAD – two dials for X-Y cursor position
– for fast scrolling – single dial on mouse
Touch-sensitive screen
•
Detect the presence of finger or stylus on the screen.
– works by interrupting matrix of light beams, capacitance
changes or ultrasonic reflections
– direct pointing device
•
Advantages:
– fast, and requires no specialized pointer
– good for menu selection
– suitable for use in hostile environment: clean and safe from
damage.
•
Disadvantages:
– finger can mark screen
– imprecise (finger is a fairly blunt instrument!)
• difficult to select small regions or perform accurate drawing
– lifting arm can be tiring
5
Stylus and light pen
Stylus
– small pen-like pointer to draw directly on screen
– may use touch sensitive surface or magnetic detection
– used in PDA, tablets PCs and drawing tables
Digitizing tablet
• Mouse like-device with cross hairs
• used on special surface
- rather like stylus
Light Pen
– now rarely used
– uses light from screen to detect location
• very accurate
- used for digitizing maps
BOTH …
– very direct and obvious to use
– but can obscure screen
Eyegaze
Cursor keys
• control interface by eye gaze direction
• Four keys (up, down, left, right) on keyboard.
• Very, very cheap, but slow.
• Useful for not much more than basic motion for textediting tasks.
• No standardized layout, but inverted “T”, most common
– e.g. look at a menu item to select it
• uses laser beam reflected off retina
– … a very low power laser!
• potential for hands-free control
• high accuracy requires headset
• cheaper and lower accuracy devices
available
like a small webcam positioned
under the screen
Discrete positioning controls
• in phones, TV controls etc.
– cursor pads or mini-joysticks
– discrete left-right, up-down
– mainly for menu selection
display devices
bitmap screens (CRT & LCD)
large & situated displays
digital paper
6
bitmap displays
resolution and color depth
• screen is vast number of coloured dots
• Resolution … used (inconsistently) for
– number of pixels on screen (width x height)
• e.g. SVGA 1024 x 768, PDA perhaps 240x400
– density of pixels (in pixels or dots per inch - dpi)
• typically between 72 and 96 dpi
• Aspect ratio
– ration between width and height
– 4:3 for most screens, 16:9 for wide-screen TV
• Color depth:
–
–
–
–
anti-aliasing
Jaggies
–
diagonal lines that have discontinuities in due to horizontal
raster scan process.
Anti-aliasing
–
–
how many different colors for each pixel?
black/white or greys only
256 from a pallete
8 bits each for red/green/blue = millions of colors
Cathode ray tube
• Stream of electrons emitted from electron gun, focused
and directed by magnetic fields, hit phosphor-coated
screen which glows
• used in TVs and computer monitors
softens edges by using shades of line colour
also used for text
electron beam
electron gun
focussing and
deflection
phosphorcoated screen
Health hints …
Liquid crystal displays
• do not sit too close to the screen
• do not use very small fonts
• do not look at the screen for long periods
without a break
• do not place the screen directly in front of a
bright window
• work in well-lit surroundings
•
Smaller, lighter, and … no radiation problems.
•
Found on PDAs, portables and notebooks,
… and increasingly on desktop and even for home TV
•
also used in dedicted displays:
digital watches, mobile phones, HiFi controls
•
How it works …
 Take extra care if pregnant.
but also posture, ergonomics, stress
– Top plate transparent and polarised, bottom plate reflecting.
– Light passes through top plate and crystal, and reflects back to
eye.
– Voltage applied to crystal changes polarization and hence color
– light reflected not emitted => less eye strain
7
special displays
large displays
Random Scan (Directed-beam refresh, vector display)
• used for meetings, lectures, etc.
• technology
–
–
–
–
draw the lines to be displayed directly
no jaggies
lines need to be constantly redrawn
rarely used except in special instruments
Direct view storage tube (DVST)
– Similar to random scan but persistent => no flicker
– Can be incrementally updated but not selectively erased
– Used in analogue storage oscilloscopes
plasma
– usually wide screen
video walls – lots of small screens together
projected
– RGB lights or LCD projector
– hand/body obscures screen
– may be solved by 2 projectors + clever software
back-projected
– frosted glass + projector behind
situated displays
Hermes: a situated display
• displays in ‘public’ places
– large or small
– very public or for small group
• display only
– for information relevant to location
• or interactive
http://www.comp.lancs.ac.uk/~fittond/hermes/about.html
• small displays beside office doors
• handwritten notes left using stylus
• office
owner reads notes using web interface
small
displays
beside
office doors
– use stylus, touch sensitive screem
• in all cases … the location matters
– meaning of information or interaction is related to
the location
handwritten
notes left
using stylus
office owner
reads notes
using web interface
Digital paper
• what?
– thin flexible sheets
– updated electronically
– but retain display
appearance
cross
section
virtual reality and 3D interaction
• how?
– small spheres turned
– or channels with coloured liquid
and contrasting spheres
– rapidly developing area
positioning in 3D space
moving and grasping
seeing 3D (helmets and caves)
8
positioning in 3D space
pitch, yaw and roll
• cockpit and virtual controls
– steering wheels, knobs and dials … just like real!
yaw
• the 3D mouse
– six-degrees of movement: x, y, z + roll, pitch, yaw
• data glove
– fiber optics used to detect finger position
• VR helmets
– detect head motion and possibly eye gaze
• whole body tracking
pitch
roll
– accelerometers strapped to limbs or reflective dots
and video processing
3D displays
VR headsets
• desktop VR
• small TV screen for each eye
• slightly different angles
• 3D effect
– ordinary screen, mouse or keyboard
control
– perspective and motion give 3D effect
• seeing in 3D
– use stereoscopic vision
– VR helmets
– screen plus shuttered specs, etc.
also see extra slides on 3D vision
VR motion sickness
simulators and VR caves
• time delay
•
•
•
•
•
– move head … lag … display moves
– conflict: head movement vs. eyes
• depth perception
– headset gives different stereo distance
– but all focused in same plane
– conflict: eye angle vs. focus
scenes projected on walls
realistic environment
hydraulic rams!
real controls
other people
• conflicting cues => sickness
– helps motivate improvements in
technology
9
dedicated displays
• analogue representations:
– dials, gauges, lights, etc.
physical controls, sensors etc.
• digital displays:
– small LCD screens, LED lights, etc.
special displays and gauges
sound, touch, feel, smell
physical controls
environmental and bio-sensing
• head-up displays
– found in aircraft cockpits
– show most important controls
… depending on context
Sounds
Touch, feel, smell
• beeps, bongs, clonks, whistles and
whirrs
• touch and feeling important
• used for error indications
• confirmation of actions e.g. keyclick
– in games … vibration, force feedback
– in simulation … feel of surgical instruments
– called haptic devices
• texture, smell, taste
– current technology very limited
BMW iDrive
http://www.bmwworld.com/technology/idrive.htm
• for controlling menus
• feel small ‘bumps’ for each item
• makes it easier to select options by feel
• uses haptic technology from Immersion Corp.
physical controls
• specialist controls needed …
– industrial controls, consumer products,
etc.
easy-clean
smooth buttons
large buttons
multi-function
control
clear dials
tiny buttons
10
Environment and bio-sensing
• sensors all around us
– car courtesy light – small switch on door
– ultrasound detectors – security,
washbasins
– RFID security tags in shops
– temperature, weight, location
• … and even our own bodies …
– iris scanners, body temperature, heart
rate, galvanic skin response, blink rate
paper: printing and scanning
print technology
fonts, page description, WYSIWYG
scanning, OCR
Printing
Types of dot-based printers
• image made from small dots
• dot-matrix printers
– allows any character set or graphic to be
printed,
• critical features:
– resolution
• size and spacing of the dots
• measured in dots per inch (dpi)
– speed
• usually measured in pages per minute
– cost!!
Fonts
– use inked ribbon (like a typewriter
– line of pins that can strike the ribbon, dotting the paper.
– typical resolution 80-120 dpi
• ink-jet and bubble-jet printers
– tiny blobs of ink sent from print head to paper
– typically 300 dpi or better .
• laser printer
– like photocopier: dots of electrostatic charge deposited on
drum, which picks up toner (black powder form of ink)
rolled onto paper which is then fixed with heat
– typically 600 dpi or better.
Fonts (ctd)
• Font – the particular style of text
Courierfont
Helvetica font
Palatino font
Times Roman font
§´v{€ƒ …€a (special symbol)
• Size of a font measured in points (1 pt about 1/72”)
(vaguely) related to its height
This is ten point Helvetica
This is twelve point
This is fourteen point
This is eighteen point
and this is twenty-four point
Pitch
– fixed-pitch – every character has the same width
e.g. Courier
– variable-pitched – some characters wider
e.g. Times Roman – compare the ‘i’ and the “m”
Serif or Sans-serif
– sans-serif – square-ended strokes
e.g. Helvetica
– serif – with splayed ends (such as)
e.g. Times Roman or Palatino
11
Readability of text
Page Description Languages
• lowercase
• Pages very complex
– easy to read shape of words
• UPPERCASE
– better for individual letters and non-words
e.g. flight numbers: BA793 vs. ba793
• serif fonts
– helps your eye on long lines of printed text
– but sans serif often better on screen
– different fonts, bitmaps, lines, digitized photos, etc.
• Can convert it all into a bitmap and send to the printer
… but often huge !
• Alternatively Use a page description language
– sends a description of the page can be sent,
– instructions for curves, lines, text in different styles, etc.
– like a programming language for printing!
• PostScript is the most common
Screen and page
Scanners
• WYSIWYG
• Take paper and convert it into a bitmap
– what you see is what you get
– aim of word processing, etc.
• but …
– screen: 72 dpi, landscape image
– print: 600+ dpi, portrait
• Two sorts of scanner
– flat-bed: paper placed on a glass plate, whole page
converted into bitmap
– hand-held: scanner passed over paper, digitising strip
typically 3-4” wide
• can try to make them similar
but never quite the same
• so … need different designs, graphics etc, for
screen and print
• Shines light at paper and note intensity of reflection
Scanners (ctd)
Optical character recognition
Used in
• OCR converts bitmap back into text
• different fonts
– desktop publishing for incorporating
photographs and other images
– document storage and retrieval systems,
doing away with paper storage
+ special scanners for slides and
photographic negatives
– colour or greyscale
• Typical resolutions from 600–2400 dpi
– create problems for simple “template
matching” algorithms
– more complex systems segment text,
decompose it into lines and arcs, and
decipher characters that way
• page format
– columns, pictures, headers and footers
12
Paper-based interaction
• paper usually regarded as output only
• can be input too – OCR, scanning, etc.
memory
• Xerox PaperWorks
– glyphs – small patterns of /\\//\\\
• used to identify forms etc.
• used with scanner and fax to control applications
• more recently
– papers micro printed - like wattermarks
• identify which sheet and where you are
– special ‘pen’ can read locations
short term and long term
speed, capacity, compression
formats, access
• know where they are writing
Short-term Memory - RAM
Long-term Memory - disks
• Random access memory (RAM)
• magnetic disks
– on silicon chips
– 100 nano-second access time
– usually volatile (lose information if power turned
off)
– data transferred at around 100 Mbytes/sec
• Some non-volatile RAM used to store basic
set-up information
• Typical desktop computers:
256 to 1024 Mbytes RAM
– floppy disks store around 1.4 Mbytes
– hard disks typically 40 Gbytes to 100s of Gbytes
access time ~10ms, transfer rate 100kbytes/s
• optical disks
– use lasers to read and sometimes write
– more robust that magnetic media
– CD-ROM
- same technology as home audio, ~ 600 Gbytes
– DVD - for AV applications, or very large files
Blurring boundaries
speed and capacity
• PDAs
• what do the numbers mean?
– often use RAM for their main memory
• Flash-Memory
– used in PDAs, cameras etc.
– silicon based but persistent
– plug-in USB devices for data transfer
• some sizes
(all uncompressed)
…
– HCI book, text only ~ 320,000 words, 2Mb
– scanned page ~ 128 Mbytes
• (11x8 inches, 1200 dpi, 8bit greyscale)
– digital photo ~ 10 Mbytes
• (2–4 mega pixels, 24 bit colour)
– video ~ 10 Mbytes per second
• (512x512, 12 bit colour, 25 frames per sec)
13
virtual memory
Compression
• Problem:
• reduce amount of storage required
• lossless
– running lots of programs + each program large
– not enough RAM
• Solution - Virtual memory :
• text: AAAAAAAAAABBBBBCCCCCCCC
10A5B8C
• video: compare successive frames and store change
– store some programs temporarily on disk
– makes RAM appear bigger
• lossy
– recover something like original – e.g. JPEG, MP3
– exploit perception
• But … swapping
– program on disk needs to run again
– copied from disk to RAM
– slows
t h i n g s
d o
– recover exact text or image – e.g. GIF, ZIP
– look for commonalities:
• JPEG: lose rapid changes and some colour
• MP3: reduce accuracy of drowned out notes
w
n
Storage formats - text
Storage formats - media
• ASCII - 7-bit binary code for to each letter and
character
• UTF-8 - 8-bit encoding of 16 bit character set
• RTF (rich text format)
- text plus formatting and layout information
• SGML (standardized generalized markup language)
- documents regarded as structured objects
• XML (extended markup language)
- simpler version of SGML for web applications
• Images:
– many storage formats :
(PostScript, GIFF, JPEG, TIFF, PICT, etc.)
– plus different compression techniques
(to reduce their storage requirements)
• Audio/Video
– again lots of formats :
(QuickTime, MPEG, WAV, etc.)
– compression even more important
– also ‘streaming’ formats for network delivery
methods of access
• large information store
– long time to search => use index
– what you index -> what you can access
• simple index needs exact match
• access without structure …
– free text indexing (all the words in a document)
– needs lots of space!!
processing and networks
finite speed (but also Moore’s law)
limits of interaction
networked computing
14
Finite processing speed
• Designers tend to assume fast processors, and make
interfaces more and more complicated
• But problems occur, because processing cannot keep up
with all the tasks it needs to do
– cursor overshooting because system has buffered
keypresses
– icon wars - user clicks on icon, nothing happens, clicks on
another, then system responds and windows fly
everywhere
• Also problems if system is too fast - e.g. help screens
may scroll through text much too rapidly to be read
Moore’s law
• computers get faster and faster!
• 1965 …
– Gordon Moore, co-founder of Intel, noticed a
pattern
– processor speed doubles every 18 months
– PC … 1987: 1.5 Mhz, 2002: 1.5 GHz
• similar pattern for memory
– but doubles every 12 months!!
– hard disk … 1991: 20Mbyte : 2002: 30 Gbyte
• baby born today
– record all sound and vision
– by 70 all life’s memories stored in a very small
storage media
the myth of the infinitely
fast machine
Limitations on interactive
performance
Computation bound
• implicit assumption … no delays
an infinitely fast machine
• what is good design for real machines?
• good example … the telephone :
–
–
–
–
type keys too fast
hear tones as numbers sent down the line
actually an accident of implementation
emulate in design
Networked computing
Networks allow access to …
– large memory and processing
– other people (groupware, email)
– shared resources – esp. the web
Issues
– network delays – slow feedback
– conflicts - many people update data
– unpredictability
– Computation takes ages, causing frustration for the user
Storage channel bound
– Bottleneck in transference of data from disk to memory
Graphics bound
– Common bottleneck: updating displays requires a lot of
effort - sometimes helped by adding a graphics coprocessor optimized to take on the burden
Network capacity
– Many computers networked - shared resources and files,
access to printers etc. - but interactive performance can
be reduced by slow network speed
The internet
• history …
– 1969: DARPANET US DoD, 4 sites
– 1971: 23; 1984: 1000; 1989: 10000
– Today?
• common language (protocols):
– TCP – Transmission Control protocol
• lower level, packets (like letters) between machines
– IP – Internet Protocol
• reliable channel (like phone call) between programs
on machines
– email, HTTP, all build on top of these
15